1. Field of the Invention
The present invention relates to a method for manufacturing a flat image-display device including a plate spacer.
2. Description of the Related Art
Image display devices that use electron-releasing elements are recently being developed as substitutes for known cathode-ray-tube display devices because of low-profile, space saving, and lightweight advantages.
FIG. 4 is a schematic sectional view of a flat image-display device. In the drawing, numeral 1 denotes a rear plate, numeral 2 denoted a side wall, and numeral 3 denotes a face plate. A fluorescent screen 4 and a metal back 5 are provided on the surface of the face plate 3 facing the rear plate 1. A space 6 surrounded by the rear plate 1, the side wall 2, and the face plate 3 is maintained in about 10−4-Pa vacuum. Therefore, a spacer 7 is provided as a structure-support member for preventing the deformation of the rear plate 1 and the face plate 3 due to the pressure difference between the exterior and the interior of the vacuum vessel.
The spacer 7 is fixed to the rear plate 1 by bonding a support member (spacer support member) 9 fixed to opposite ends thereof to the rear plate 1. The rear plate 1 with the spacer 7 and the face plate 3 are fixed in alignment.
In the image display device, at the instant when electrons are released from electron-releasing elements (not shown) arranged on the rear plate 1, the electrons are accelerated by applying hundreds to thousands of volts of high voltage to the metal back 5 to collide against the face plate 3, so that fluorescent substances of the fluorescent screen 4 are excited to emit light, thereby displaying an image.
However, the known image display devices made as in FIG. 4 have the following problems.
As described above, although the opposite ends of the spacer 7 are bonded to the rear plate 1 with the spacer support member 9, the center of the spacer 7 is merely in contact with the rear plate 1 and is not fixed thereto.
Therefore, when the rear plate 1 with the spacer 7 is given an external impact by transfer or the like after the completion of assembly of the spacer 7 and the rear plate 1 before the start of the assembly of the rear plate 1 and the face plate 3, the center of the spacer 7 may be displaced from the initial assembly position.
When the center of the spacer 7 is displaced from the initial assembly position, there is a high possibility that the spacer 7 will not return to the initial position owing to the frictional resistance between the spacer 7 and the rear plate 1, thus not ensuring accuracy of spacer assembly position.
Therefore, when the rear plate 1 and the face plate 3 are joined, with the center of the spacer 7 displaced from the initial position, it may exert a bad influence on the display image, thus preventing stable production of high-quality image display devices.